Effects of compensatory growth on protein metabolism and meat tenderness of beef steers

The relationships between meat tenderness and the changes in metabolism and body composition associated with compensatory growth in cattle were examined. Thirty-six steers were randomly allotted to 12 pens of three with three diets assigned randomly to the pens. Diets were alfalfa/grass silage, alfalfa/grass silage supplemented with corn gluten and bloodmeal and corn silage supplemented with soybean meal. Six steers from each treatment were slaughtered on each of days 124 and 175 of the trial to assess carcass characteristics. Following 124 d on trial, the remaining steers received a high-grain finishing diet. Blood and urine samples were collected throughout the trial for analyses of 3-methylhistidine, hydroxyproline and creatinine. At each slaughter, non-carcass components were cleaned and weighed. Lean, fat and bone proportions were estimated with a 9th-10th-11th rib dissection. Following dissection, the longissimus muscles were frozen at −10 °C for analysis of shear force, collagen and protein solubility. The steers fed the alfalfa/grass silage experienced compensatory growth within the first 14 d of the finishing phase. Steers fed the alfalfa/grass silage had lower gain throughout the growing phase (0–124 d), and empty body weight was less than that of the steers fed corn silage. Compensatory growth was observed in steers fed corn silage during the first 14 d of the finishing diet, as evidenced by higher gains compared with steers fed the other diets. Differences in body composition among treatments at 124 d and 175 d were related to dietary energy and not compensatory growth. Meat tenderness, measured by shear force, appeared to be affected primarily by dietary energy and intramuscular fat rather than by rate of growth.